Abstract：The drop of insulation performance of insulator under icing or snow weather is one of the important causes of grid accident. Although domestic and foreign scientists had carried out many researches on icing insulators, the study on snow-covered insulators is relatively lacking. The influence of snow-covered insulators on transmission line insulation safety cannot be ignored. Therefore, it is necessary to study the performance of snow-covered insulators. Generally, there are even snow accretion and uneven snow accretion on insulators. This paper simulates natural snowing environment in the artificial climate chamber. Regarding polluted suspension glass and ceramic insulators, the influences of even and uneven snow accretions on their negative DC flashover characteristics and flashover process are compared. It is shown that the influence of uneven snow accretion on DC flashover characters is greater than that of even snow accretion when the degrees of snow accretion are the same, while in the case of heavier pollution on insulators, the influence of snow accretion shape on insulators deceases, particularly, under severe pollution, the snow accretion shape has no impacts on insulator flashover voltage. The snow flashover process is similar to pollution flashover at the initial stage while similar to ice flashover in the end. With uneven snow accretion, the flashover path develops along the leeward side of insulators.